Archer T3U Plus AC1300 Low Speed @5ghz @usb3.0

I’m using an Archer T3U Plus AC1300 adapter on a 5GHz network with a 1000/1000 Mbps plan. Even when placing the PC right next to the router, I only get ~300 Mbps in speed tests.
What I’ve Tried:
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Set 80MHz channel width and manually selected Channel 120 (DFS) in the router.
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Installed the latest drivers on Windows 11.
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Confirmed the adapter is connected via USB 3.0 (blue port).
Observations:
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Windows Wi-Fi status shows a "Link Speed" of 780 Mbps, but actual throughput is much lower (~300 Mbps).
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Speed tests were done via Ookla with no other network activity.
Questions:
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Why is the real-world speed far below the link speed?
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Could this be a driver/hardware limitation of the T3U Plus?
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Any settings (router/adapter/Windows) I might’ve missed?
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Welcome to our community.
If you're suffering from the slow speed issue with the wireless adapter, please refer to the following troubleshooting steps:
1. Connect another mobile device to the same Wi-Fi router to check whether the issue is on the router or adapter.
2. Disable the original wireless adapter from the control panel of your PC.
3. Move the computer installed the adapter about 10-15 feet to your router.
4. If you have a dual-band wireless adapter, please ensure the router supports 5 GHz and connect the wireless adapter to the 5 GHz band.
5. Change the wireless settings on the main router, like channel 1/6/11 for 2.4GHz, and channel 36/40/44/48 for 5GHz.
Best Regards.
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Hi Joseph, thank you for your reply.
I've already followed all of the suggested steps:
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✅ I tested my router with a phone and achieved 850+ Mbps download speed — so the issue is clearly not on the router or connection.
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✅ My PC doesn’t have an internal Wi-Fi adapter. I’m using only the TP-Link Archer T3U Plus, connected via USB 3.0.
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✅ The PC is placed right next to the router, with excellent signal quality.
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✅ I’m connected to the 5 GHz band, specifically channel 36, which avoids DFS restrictions.
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✅ I’ve ensured clean, low-interference channel selection and high transmit power. WPA2-AES encryption is used.
📷 I’ve also attached a screenshot of my wireless configuration for clarity.
https://drive.google.com/file/d/1KXDWuPv9I69UqQC5vOYIqJbnoxw5DIjh/view?usp=sharing
https://drive.google.com/file/d/10no4v1asOsfuxoJYCVTUPzPgXpEH-i33/view?usp=sharing
You can see that:
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5 GHz is enabled on channel 36
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I am connected via SSID6 (5GHz) as shown
Despite a link speed of 780 Mbps, the actual download speed remains stuck around 300 Mbps, even under ideal conditions.
From what I’ve gathered, the Archer T3U Plus appears to use a single antenna and 1x1 MIMO, which seems to realistically cap performance at around 300–350 Mbps.
So here’s my main question to the community:
👉 Has anyone ever reached 600–700+ Mbps real-world speed using this exact adapter (T3U Plus)?
I'm trying to confirm whether this is a common hardware limitation, or if there might be something wrong or misconfigured on my side.
Thanks again, and I appreciate any input from others who have tested this adapter.
Best regards.
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Hi,
For this type of AC Wi-Fi adapter the theoretical limit with one antenna is 433 Mbps and with two antennas 867 Mbps.
A reasonable real-world speed for the T3U Plus would be around 450 Mbps, perhaps 600 Mbps are possible in optimal conditions.
One thing that USB AC Wi-Fi adapters based on Realtek chips have in common is that support for USB 3.0 mode is somewhat patchy.
I suggest you use a software like SIV System Information Viewer or USB Device Tree Viewer to find out whether the T3U Plus is currently running in USB 3.0 mode or in USB 2.0 mode. The latter would explain why the speed is being capped at 300 Mbps. (the "mode" I am talking about is independent of the port physically being USB 3.0)
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Hi, thanks for the answer.
I've been troubleshooting my TP-Link Archer T3U Plus adapter, and noticed it only connects as USB 2.1 (High-Speed) instead of USB 3.0 (SuperSpeed).
I verified this using USB Device Tree Viewer, which shows the device is SuperSpeed-capable but only operates at High-Speed.
To rule out port issues, I tested a USB 3.0 portable hard drive on the same ports-it correctly connects at USB 3.0 speed. So I’m assuming the issue lies with the adapter itself.
I also installed the latest Realtek driver, but it didn’t change anything.
Any ideas or known issues regarding this behavior?
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Yes, this is a known issue. There have been plenty of threads about it in this forum.
Some users were able to solve it by trying various different versions of the driver, others by trying different USB 3 ports (because some computers have more than one USB 3 controller), yet some users still couldn't make it work.
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This is exactly the kind of answer I was looking for. Thanks for sharing
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